2. Introduction to Atomic Structure

3. Chemistry Chemistry is the study of matter and the changes it undergoes. The type of matter that is changing and what types of changes it undergoes determines the field of chemistry that is being studied.

4. Branches of Chemistry Physical Chemistry: the study of matter and the physics behind its changes

5. Branches of Chemistry Physical Chemistry: the study of matter and the physics behind its changes Biochemistry: the study of the makeup and changes undergone by living species

6. Branches of Chemistry Physical Chemistry: the study of matter and the physics behind its changes Biochemistry: the study of the makeup and changes undergone by living species Analytical Chemistry: The study of the composition (or analysis) of substances

7. Branches of Chemistry Physical Chemistry: the study of matter and the physics behind its changes Biochemistry: the study of the makeup and changes undergone by living species Analytical Chemistry: The study of the composition (or analysis) of substances Organic Chemistry: The study of compounds which primarily contain Carbon

8. Branches of Chemistry Physical Chemistry: the study of matter and the physics behind its changes Biochemistry: the study of the makeup and changes undergone by living species Analytical Chemistry: The study of the composition (or analysis) of substances Organic Chemistry: The study of compounds which primarily contain Carbon Inorganic Chemistry: The study of compounds which do NOT contain Carbon

9. Matter You will recall that we define matter as anything that has mass and takes up space. Atoms of an element Molecules of a diatomic element Molecules of a compound Mixture of elements and a compound

10. Dalton's Postulates Building on Democritus' idea, in the early 1800s, English chemist John Dalton was the first scientist to observe the physical world and matter and via these observations, this draw some conclusions about atoms.

11. Dalton's Four Postulates (1) Matter is made of atoms; atoms are indivisible and indestructible. (2) All atoms of one element are exactly identical to one another; atoms of different elements are different from one another. Various atoms and molecules as depicted in John Dalton's 1808 book: A New System of Chemical Philosophy

12. Dalton’s Four Postulates (4) Compounds are formed when atoms of more than one element combine; a given compound always has the same relative number and kind of atoms. Hydrogen Oxygen Water (3) Atoms of an element are not changed into atoms of a different element by chemical reactions; atoms are neither created nor destroyed in chemical reactions.

13. Law of Conservation of Mass The total mass of substances present at the end of a chemical process is the same as the mass of substances present before the process took place. click here for an explanation of conservation of mass

14. 26 Which one of the following is not one of the postulates of Dalton's atomic theory? A Atoms are made of protons, neutrons, and electrons. B All atoms of a given element are identical C Atoms are neither created nor destroyed in chemical reactions. D Compounds are formed when atoms of more than one element combine E Each element is composed of extremely small particles called atoms. 

15. Scientists

16. J. J. Thomson (1903) Discovered electron Electrons have a negative charge!! Theorized about protons

17. Made a piece of equipment called a cathode ray tube. It is a vacuum tube - all the air has been pumped out. J. J. Thomson (1903)

19. Thomson’s Experiment Voltage source +- Vacuum tube Metal Disks

20. Thomson’s Experiment Voltage source +-

21. Thomson’s Experiment Voltage source +-

22. Thomson’s Experiment Voltage source +-

23. n Passing an electric current makes a beam appear to move from the negative to the positive end Thomson’s Experiment Voltage source +-

24. n Passing an electric current makes a beam appear to move from the negative to the positive end Thomson’s Experiment Voltage source +-

25. n Passing an electric current makes a beam appear to move from the negative to the positive end Thomson’s Experiment Voltage source +-

26. n Passing an electric current makes a beam appear to move from the negative to the positive end Thomson’s Experiment Voltage source +-

27. Thomson’s Experiment By adding an MAGNETIC field

28. Voltage source Thomson’s Experiment n By adding an electric field + -

29. Voltage source Thomson’s Experiment n By adding an electric field + -

30. Voltage source Thomson’s Experiment n By adding an electric field + -

31. Voltage source Thomson’s Experiment n By adding an electric field + -

32. Voltage source Thomson’s Experiment n By adding an MAGNETIC field + -

33. Voltage source Thomson’s Experiment n By adding an electric field he found that the moving pieces were negative + -

34. J. J. Thomson (1903) Plum-pudding Model positive sphere (pudding) with negative electrons (plums) dispersed throughout

35. JJ Thomson’s Idea He knew that the atom contained + and – charges. The atom was like “Plum Pudding” a mix of + and -.

36. Ernest Rutherford (1911) Gold Foil Experiment Discovered the nucleus The protons in the nucleus

37. Rutherford’s experiment Used radioactive alpha particles to prove the existence of protons.(He +2 ) Alpha particles (He +2 ) - positively charged pieces- helium atoms minus electrons Shot them at gold foil which can be made a few atoms thick.

38. Lead block Uranium Gold Foil Fluorescent Screen

39. What he expected

40. Because

41. He thought the mass was evenly distributed in the atom

42. What he got

43. +

44. Why did JJ believe electrons have charges?

45. Ernest Rutherford (1911) Developed the Planetary Model dense, positive nucleus surrounded by negative electrons

46. James Chadwick (1932)

47. Discovered neutrons neutral particles in the nucleus of an atom

48. Atom is mostly empty. Small dense, positive piece at center. Alpha particles are deflected by it if they get close enough.

53. Mass Number Mass number is simply the sum total of protons and neutrons in the nucleus of an atom. Recall that electrons have insignificant mass compared to protons and neutrons. C 12 6 Mass numbers are always whole numbers Mass numbers are NOT on the Periodic Table Atoms of the same element can have different mass numbers

54. Figuring out number of neutrons in an element The number of neutrons for any element can be found by subtracting the element's Atomic Number ("Z") from the element's Mass Number ("A") A - Z = Number of Neutrons Some elements can have many different numbers of neutrons. Atoms with the same Z but different A are called Isotopes.

55. Symbols Symbols on the periodic table contain the symbol (letter) of the element, the mass number and the atomic number The letter symbol refers to an atom with a specific number of protons. # protons + # neutrons mass number X Mass Number Atomic Number Remember, when the atom is neutral, the number of protons equals electrons

56. Atomic Number and Mass Number Atomic Number Number of protons Atomic Number also equals number of electrons in a neutral atom 12 6 Mass Number Atomic Number C M ass Number Number of protons + neutrons 12 C 6 14 C 6

57. 1 Find the atomic number. Na 23 11 Sodium Atom

58. 2 Find the mass number. Na 23 11 Sodium Atom

59. 3 How many protons does this element have? Na 23 11 Sodium Atom

60. 4 How many electrons does this element have? Na 23 11 Sodium Atom

61. 5 How many neutrons does this element have? Na 23 11 Sodium Atom

62. 6 Find the atomic number. Br 80 35 Bromine Atom

63. 7 Find the mass number. Br 80 35 Bromine Atom

64. 8 How many protons does this element have? Br 80 35 Bromine Atom

65. 9 How many electrons does this element have? Br 80 35 Bromine Atom

66. 10 How many neutrons does this element have? Br 80 35 Bromine Atom

67. 1 The atomic number indicates __________. A the number of neutrons in a nucleus B the total number of neutrons and protons in a nucleus C the number of protons or electrons in a neutral atom D the number of atoms in 1 g of an element E I don't know how to answer this question.